Extraction of sugar from sugarcontaining liquids



Patented Nov. 22, 1949 OFFICE EXTRACTION OF SUGAR FROM SUGAR- CONTAININGLIQUIDS Josef Hradecky, Bregenz, Vorarlberg, Austria, as-

signor to Hans Ginter and Hans Manzoni, both of Vienna, Austria NoDrawing. Application July 15, 1947, Serial No. 761,141. In AustriaAugust 12, 1946 8 Claims. 1

This invention relates to a process for the extraction of sugar frommolasses and other sugar containing liquids.

It is known, for this purpose, to treat the molasses with bariumhydroxide under heat, generally between 85 and 100 C., in order toprecipitate barium saccharate, which is decomposed by carbon dioxideinto barium carbonate and sugar solution. The methods hitherto proposed,however, have had little success in practice because the bariumsaccharate is incompletely separated out, and above all in a form inwhich the precipitate can only be separated from the residual solutionwith great difficulty.

The principal object of the present invention is to provide a processfor recovering sugar from molasses or similar sugar containing liquidswhile using barium hydroxide as precipitating agent which processenables to extract the sugar present in such solutions in a higherpercentage than heretofore. Another object of the invention is toprovide a method by which the sugar present in molasses or other sugarcontaining liquids is precipitated in the form of a crystalline mass ofbarium saccharate, which can be readily filtered oii from the wasteliquor.

Other objects of the invention will appear as the description proceeds.

The process according to the invention consists substantially in addingbarium hydroxide to the sugar containing liquids from which the sugar isto be extracted, while adjusting the concentration of barium ions so asto lie above the product of solubility of mono-barium saccaharate,initiating the crystallization of mono-barium saccharate by graftin withcrystals of monobarium saccharate and maintaining the supersaturation ofthe solution with barium ions by the addition of barium hydroxide duringthe crystallization according to the quantity of barium ions consumed inthe formation of monobarium saccharate.

The grafting with crystals of mono-barium saccharate, which is ofessential importance to the process according to the invention, ispreferabl effected with crystals of mono-barium saccharate which hasbeen separately produced from pure sugar and pure barium hydroxide.

The process according to the invention may, for example, be carried outin the following manner:

Hot barium hydroxide solution is added to the slightly dilute molasseswith simultaneous cooling. The temperature of the mixtureshouldadvantageously be below 50 C. and is preferably so controlled thatit is at about 20 C. The quantity of barium hydroxide solution added issuch, having regard to the sugar content of the molasses and theconcentration of the barium hydroxide solution, that the concentrationof barium ions at the working temperature lies above the product ofsolubility of the mono-barium saccharate, that is to say, asuper-saturated solution in respect of barium ions is obtained. Thsupersaturated molasses are then grafted with crystals of mono-bariumsaccharate, which are preferably cultivated from pure sugar and bariumhydroxide. The quantity of grafting material is such that sufiicientcrystal surface is available for the crystallization set up and that nouncontrolled formation of new crystals occurs under the conditions ofcrystallization produced, but that the crystals merely grow. When thecrystallization has started, barium hydroxide solution is added,according to the quantity of barium ions disappearing owing to theformation of mono-barium saccharate, in such a quantity in each casethat there is always a slight supersaturation with barium ions, so thata controlled progress of the crystallization is ensured. In order tocheck and control this process, the pH- value of the solution, whichmust lie in the alkaline zone, is constantly observed during thecrystallization. The addition of barium hydroxide therefore takes placein such a manner that the pI-I-value is kept substantially constantuntil near the end of the crystallization process. The end of thecrystallization is marked by a sudden increase in the pH-value owing tothe cessation of the formation of saccharate. At this moment, theaddition of barium hydroxide is discontinued. The precipitate ofmono-barium saccharate formed is filtered off from the residualsolution, for example by the aid of filter presses, and is subsequentlywashed with a dilute barium hydroxide solution, for example with acold-saturated barium hydroxide solution or a hot 2-3% barium hydroxidesolution. The washing liquid is taken up separately and can be used todilute the molasses in the following operation.

The extraction of the sugar may be carried to any desired degree bysuitable selection of the final concentration of barium ions. Up to97.2%, referred to the sugar present, can rationally be extracted at themaximum. However, it is preferable to operate in such a manner thatrafinose present, which has a tendency to precipitate at the same time'at high barium ion concentrations, remains in solution. If in someparticular case the waste liquor still contains sugar, this sugar can beprecipitated as bi-barium saccharate by adding Ba(OH)z and heating totemperatures above 60 0., this bi-barium saccharate being filtered oifand employed in the next operation.

The mono-barium saccharate yielded as a filter cake is decomposed intosugar solution and barium carbonate after being worked up into a pastewith pure water at boiling temperature with CO2 or waste gasescontaining C02. The slight residue of barium ions is precipitated by theaddition of dilute sulphuric acid. In order also to remove the lasttraces of barium hydroxide which cannot be precipitated with sulphuricacid owing to the danger of exceeding the neutral point, (NI-102804 isadded until the barium reaction ceases. The pure sugar solution yieldedin the decomposition may if necessary be treated with active charcoal,filtered off and evaporated. The barium carbonate formed in thecarbonatation may also be worked up again into barium hydroxide by knownmethods, for example by decomposing it with hydrochloric acid with theaid of anti-foaming agents and employing the carbon dioxide formed forthe carbonatation. The barium chloride yielded can be converted intoBa(OI-I)z by electrolyses and returned into the process.

The excess barium hydroxide can also be precipitated by C02 from thewaste liquor from which the sugar has been extracted, whereafter thewaste liquor, now free from barium, can be worked up into chemicalsafter evaporation.

I claim:

1. A process for the extraction of sugar from sugar containing liquidscomprising the steps of adding barium-hydroxide to the sugar containingliquid while adjusting the concentration of barium ions so as to lieslightly above the product of solubility of mono-barium saccharate,grafting the said liquid supersaturated in respect of barium ions withcrystals of mono-barium saccharate, adding barium hydroxide during thecrystallization according to the quantity of barium ions consumed by theformation of monobarium saccharate to maintain the supersaturation ofthe liquid with barium ions during the crystallization, saidcrystallization being effected at a temperature between 50 C. and C.,separating the crystalline barium saccharate precipitated from the wasteliquor, washing and carbonating it.

2. A process for the recovery of sugar from molasses comprisingcultivating crystals of monobarium saccharate from pure solutions ofbarium hydroxide and of sugar, grafting molasses supersaturated withrespect to barium ions with said crystals, maintaining the concentrationof barium ions in said solution until no further formation ofmono-barium saccharate occurs, maintaining the temperature of the saidgrafted solution between 50 C. and 20 0., separating the precipitatedmono-barium saccharate and carbonating it.

3. A process for the extraction of sugar from a sugar containing liquidcomprising adding barium-hydroxide to said liquid while continuouslyadjusting the concentration of barium ions to a point slightly above theproduct of solubility of mono-barium saccharate, grafting the saidliquid supersaturated with barium ions with crystals of mono-bariumsaccharate to control crystallization of precipitated mono-bariumsaccharate, continuing the said adjustment of barium ions by theaddition of barium-hydroxide during the said crystallization, saidcrystallization being effected at a temperature below 50 C., separatingthe precipitated crystalline barium saccharate, washing and carbonatingit.

4. In a process for the extraction of sugar from sugar containingliquids adding barium-hydroxide to the sugar containing liquid whileadjusting the concentration of barium ions 50 as to lie slightly abovethe product of solubility of monobarium saccharate, grafting the saidliquid supersaturated in respect of barium ions with crystals ofmono-barium saccharate, adding barium hy droxide during thecrystallization according to the quantity of barium ions consumed by theformation of mono-barium saccharate to maintain the supersaturation ofthe liquid with barium ions during the crystallization, saidcrystallization of mono-barium saccharate being eiiected between 50 C.and 20 C., separating the crystalline barium saccharate precipitatedfrom the waste liquor, washing and carbonating it.

5. A process for the extraction of sugar from a sugar containing liquidcomprising adding baium hydroxide to to said liquid in amount necessaryto adjust the concentration of barium ions to a point slightly above theproduct of solubility of mono-barium saccharate, determining the pHvalue of said liquid, grafting said liquid with crystals of mono-bariumsaccharate to control crystallization of precipitated monobariumsaccharate, adding barium hydroxide during said crystallization tomaintain said determined pH value, discontinuing the addition of bariumhydroxide upon sudden substantial increase in said pH value efiectingsaid crystallization between 50 C. and 20 C., separating precipitatedcrystalline mono-barium saccharate, washing and carbonating it.

6. A process for the extraction of sugar from a sugar containing liquidcomprising adding barium hydroxide to said liquid in amount necessary toadjust the concentration of barium ions to a point slightly above theproduct of solubility of mono-barium saccharate, determining the pHvalue of said liquid, grafting said liquid with crystals of mono-bariumsaccharate to control crystallization of precipitated mono-bariumsaccharate, said crystallization being eiiected at a temperature below50 0, adding barium hydroxide during said crystallization to maintainsaid determined pH value, discontinuing the addition of barium hydroxideupon sudden substantial increase in said pH value, separatingprecipitated crystalline mono-barium saccharate, washing and carbonatingit.

'7. A process for the recovery of sugar from mo lasses comprisingcultivating crystals of barium mono-saccharate from pure solutions ofbarium hydroxide and of sugar, grafting molasses supersaturated inrespect of barium ions with said crystals maintaining the concentrationof barium ions in said solution until no further formation of bariumsaccharate occurs, said crystallization of mono-barium saccharate beingefiected between 50 C. and 20 0., separating the precipitated bariumsaccharate and carbonating it.

8. A process for the extraction of sugar from a molasses solutioncomprising the addition of barium hydroxide to said solution in amountnecessary to maintain the barium ion concentration above the product ofsolubility of monobarium saccharate, grafting said solution withcrystals of mono-barium saccharate formed from pure solution of bariumhydroxide and sugar to control crystallization of precipitatedmonobarium saccharate, maintaining said barium ion concentration byfurther addition of barium hydroxide until no further precipitationoccurs,

effecting said crystallization between 50 C. and Number 260,244 20 C.,separatmg sald preclpltated mono-barium 279 446 saccharate andcarbonating it. 5 2941159 1,878,144 JOSEF HRADECKY. 1,878,145

REFERENCES CITED The following references are of record in the 101:970:605

file of this patent:

6 UNITED STATES PATENTS Name Date Scheibler June 27, 1882 Scheibler June12, 1883 Stefien Feb. 26, 1884 Holven Sept. 20, 1932 Holven Sept. 20,1932 Meade et a1 Oct. 25, 1932 Spencer Oct. 25, 1932 I-Iixon et a1. Aug.21, 1934 OTHER REFERENCES Fairrle: Sugar," first ed., Liverpool 1925,page

